1. Field of Invention
This invention pertains generally to inertial sensors including gyroscopes and more particularly gyroscopes based on ensembles of negatively charged nitrogen-vacancy centers in diamonds.
2. Background
Recent decades have seen an increased demand for low cost, accurate and reliable control and navigation systems for land, sea and space vehicles. These systems are typically based on gyroscopes or inertial sensors that can measure precisely changes in the orientation of the vehicle or device as it moves. Such devices also find use in gravity research, for example, in tests of Einstein's equivalence principle or to search for the Lens-Thirring effect, a prediction from general relativity of “framedragging” in the presence of a massive rotating body.
Gyroscopes are physical sensors that detect and measure the angular motion of an object in relation to an internal frame of reference. The gyroscope was named by French physicist, Jean Bernard Leon Foucault, who attempted to demonstrate the rotation of the Earth in 1852.
Early gyroscopes were spinning disks on a central axel inside of a stable frame. The rotor spins on a fixed axis while the frame around the rotating disk can rotate or tilt. The spinning disk resists changes to its axis of rotation. When the axis of the spinning rotor is tilted perpendicularly to the direction of the spin, the axis will precess. Precession keeps the spinning rotor in a vertical orientation while the structure around the rotor tilts with the reference surface. The angle of the rotor axis relative to the reference structure can also be measured.
Another approach includes microelectromechanical systems (MEMS) vibrating mass gyroscopes aimed at creating smaller, more sensitive devices. The vibrating mass approach exploits the exchange of energy between different axes of vibration due to the Coriolis effect. MEMS vibratory gyroscopes measure rotation rate by vibrating a proof-mass and sensing the Coriolis force caused by angular velocity. Vibrating mechanical elements (proof-mass) have no rotating parts that require bearings and they can be easily fabricated using micromachining techniques.
Present state-of-the-art sensors used for navigation in the airline industry are based on the Sagnac effect in fiber-optic bundles, with sensitivities at the level of 2×10−8 rad s−1 Hz−1/2. The same effect in large-area (˜m2) ring lasers has yielded a sensitivity at the level of 2×10−10 rad s−1 Hz−1/2 . Gyroscopes based on cold atom interferometry have also demonstrated sensitivity in the range of 10−9 to 10−10 rad s−1 Hz−1/2. Noble gas nuclear spins, which feature long coherence times, can also be used to form rotation sensors and have a demonstrated sensitivity of about 3×10−7 rad s−1 Hz−1/2. Variations on this scheme yield a projected sensitivity in the range of 10−10 rad s−1 Hz−1/2 in an active volume of several cubic centimeters. This concept has been extended to miniaturized versions. Finally, commercially available vibrating microelectromechanical system (MEMS) gyroscopes achieve sensitivities of the order of 2×10−4 rad s−1 Hz−1/2. Except for the latter two cases, these sensors rely on large volumes or enclosed areas.
In spite of the sensitivity advantages of MEMS based gyroscopes, they suffer from sensitivity drifts that can arise after a few minutes of operation from temperature variations and noise making them unattractive for several conventional applications. However, to achieve sensitivities that are comparable to MEMS, other systems used as gyroscopes typically require large volumes (˜cm3), long startup times, as well as large power and space requirements.
Accordingly, there is a need for sensitive and reliable gyroscope systems that are resistant to vibrations, temperature variations and have relatively small size requirements. The present invention satisfies these needs as well as others and is generally an improvement over the art.